Heat resistant resin composition

ABSTRACT

A heat resistant resin composition comprising from 10 to 90% by weight of a copolymer A and from 90 to 10% by weight of a copolymer B, in which the copolymer A is composed of an N-aromatic maleimide monomer residue, a maleimide monomer residue, a vinyl aromatic monomer residue and, optionally other vinyl monomer residue, the total content of the N-aromatic maleimide monomer residue and the maleimide monomer residue being from 10 to 45%, the content of the N-aromatic maleimide monomer residue being greater than the content of the maleimide monomer residue, the content of the vinyl aromatic monomer residue being from 90 to 55% and the content of said other vinyl monomer residue being from 0 to 20%, and the copolymer B is composed of a vinyl cyanide monomer residue, a vinyl aromatic monomer residue and, optionally other vinyl monomer residue, the content of the vinyl cyanide monomer residue being from 20 to 55%, the content of the vinyl aromatic monomer residue being from 80 to 45% and the content of said other vinyl monomer residue being from 0 to 20%.

The present invention relates to a heat resistant resin compositionhaving a high thermal deformation temperature and a high thermaldecomposition temperature.

A copolymer (SMA) of a vinyl aromatic monomer with maleic anhydride hasa high thermal deformation temperature and good compatibility with otherthermoplastic resins such as a styreneacrylonitrile copolymer (ASresin), and it is useful for the preparation of a heat resistant resincomposition.

However, SMA is inferior in its stability at a high temperature, and ithas drawbacks that when heated at a temperature of 230° C. or higher, ittends to lead to foaming or weight reduction and it is likely to undergocross-linking, whereby the molding processability of the resincomposition containing SMA is considerably impaired. It has beenattempted to improve the high temperature stability of SMA byincorporating various additives such as anti-oxidants, but nosatisfactory results have been obtained. The present inventors haveconducted extensive researches with an aim to overcome theabove-mentioned drawbacks and to present a heat resistant resincomposition containing a copolymer composed of a vinyl aromatic monomerand a maleic acid derivative and having a high temperature stability anda high thermal deformation temperature. As a result, the presentinvention has been accomplished.

Namely, the above-mentioned object of the present invention has beenattained by a heat resistant resin composition comprising from 10 to 90%by weight of a copolymer A and from 90 to 10% by weight of a copolymerB, in which the copolymer A is composed of an N-aromatic maleimidemonomer residue, a maleimide monomer residue, a vinyl aromatic monomerresidue and, optionally other vinyl monomer residue, the total contentof the N-aromatic maleimide monomer residue and the maleimide monomerresidue being from 10 to 45%, the content of the N-aromatic maleimidemonomer residue being greater than the content of the maleimide monomerresidue, the content of the vinyl aromatic monomer residue being from 90to 55% and the content of said other vinyl monomer residue being from 0to 20%, and the copolymer B is composed of a vinyl cyanide monomerresidue, a vinyl aromatic monomer residue and, optionally other vinylmonomer residue, the content of the vinyl cyanide monomer residue beingfrom 20 to 55%, the content of vinyl aromatic monomer residue being from80 to 45% and the content of said other vinyl monomer residue being from0 to 20%.

In the present invention, the content of each monomer residue isrepresented by a proportion by percentage of the number of units of themonomer residue to the total number of units of various monomer residuescontained in the copolymer concerned.

Now, the present invention will be described in detail with reference tothe preferred embodiments.

As the vinyl aromatic compound to be used in the present invention,styrene is most common, but other compounds such as α-methylstyrene,p-methylstyrene, t-butylstyrene, a styrene halogenide or a mixturethereof may be used. As the vinyl cyanide compound, acrylonitrile,methacrylonitrile or a mixture thereof is usually used.

The N-aromatic maleimide may be obtained by condensing a primaryaromatic amine with fumaric acid, maleic acid, maleic acid anhydride orother maleic acid derivatives. As the primary aromatic amine, aniline oran aniline derivative with its benzene ring substituted by an alkylgroup, a halogen atom or a nitro group, such as toluidine ornitroaniline is used. Further, phenylenediamine or α-naphthylamine mayalso be used. These amines may be used alone or in combination as amixture of two or more different kinds. The maleimide may be obtained bycondensing a maleic acid derivative such as maleic acid anhydride, withammonia. The copolymer A may be produced by copolymerizing an N-aromaticmaleimide with other monomers. However, as will be mentionedhereinafter, it is preferred to employ a method wherein a maleic acidanhydride copolymer is reacted with the above-mentioned amine andammonia during the polymerization step or in a separate step to convertit into an imide, since this method is simple and the required monomersare readily available.

The content of the N-aromatic maleimide in the copolymer A must begreater than the content of the maleimide. Otherwise, the compatibilityof the copolymer A with the copolymer B will be poor, thus leading to aninferior physical properties of the resin composition thereby obtained.Within the above-mentioned range, the greater the content of themaleimide residue is, the higher the thermal deformation temperaturebecomes.

The total content of the N-aromatic maleimide residue and the maleimideresidue contained in the copolymer A should be from 10 to 45%. If thetotal amount exceeds 45%, the flowability tends to decrease and themolding operation becomes difficult. On the other hand, if the totalamount is less than 10%, no adequate improvement of the thermaldeformation temperature is obtainable.

Further, the content of the vinyl aromatic monomer residue should befrom 90 to 55%. If the content of the vinyl aromatic monomer residueincreases, the flowability will be improved, but the thermal deformationtemperature decreases.

A part of the vinyl aromatic monomer residue may be replaced by othermonomer, for instance, a vinyl cyanide monomer such as acrylonitrile ormethacrylonitrile, an ester of acrylic acid or methacrylic acid such asmethylacrylate or methylmethacrylate, or a derivative of maleic acid orfumaric acid such as maleic anhydride, dimethyl maleate or dimethylfumarate, as the case requires. In such a case, the content of the othermonomer for replacement should be at most 20%. If the content exceeds20%, the compatibility with other styrene-type resin is likely to beinferior.

Adequate compatibility with the copolymer A will be obtained if thecontent of the vinyl cyanide monomer residue in the copolymer B iswithin a range of from 20 to 55%, the rest being the vinyl aromaticmonomer residue.

A part of the vinyl aromatic monomer residue may preferably besubstituted by other vinyl monomer such as an ester of acrylic acid ormethacrylic acid, as the case requires. In such a case, the content ofsaid other vinyl monomer residue should preferably be at most 20%,whereby no adverse effects will be imparted to the compatibility withother resins.

The composition according to the present invention is superior in theheat resistance, high temperature stability, solvent resistance andflowability during the molding operation. Further, the composition ofthe present invention has good compatibility with an ABS resin, a MBSresin, an AES resin, an ACS resin or an AAS resin, and accordingly it ispossible to improve the shock resistance by incorporating such resins.In such a case, it is readily possible to bring the thermal deformationtemperature (a Vicat softening point) to at least 115° C. Further, areinforcing material or filler such as glass fiber, carbon fiber, talcor calcium carbonate, or other additives may be incorporated.

Now, the process of the present invention will be described. Firstly,bulk polymerization is conducted while continuously supplying maleicacid anhydride in the presence of the vinyl aromatic monomer. The amountof the maleic acid anhydride monomer to be added here is preferably from10 to 45 molar %. The polymerization temperature is preferably from 90°to 130° C., and no polymerization initiator may be required. Theconversion in this step is at least 10% by weight and can be increasedas far as the stirring driving force of the polymerization apparatuspermits. The polymerization time is determined depending upon theconversion, the polymerization temperature, the concentration of themaleic acid anhydride, and is usually within a range of from 1 to 10hours. After completion of the continuous supply of the maleic acidanhydride, the maleic acid anhydride in the monomer mixture will rapidlybe consumed, whereupon the system becomes in the form of a syrupcomposed substantially of the copolymer and the vinyl aromatic monomer.A part of the vinyl aromatic compound to be initially present may bereplaced by an ester of acrylic acid, an ester of methacrylic acid or avinyl cyanide compound.

To this syrup, a vinyl cyanide monomer is added and uniformly mixed. Theamount of the addition is adjusted to bring the content of the vinylcyanide monomer residue in the copolymer formed by the reaction with theremaining vinyl aromatic compound to a level of from 20 to 55%.

This syrup is suspended in water, and the vinyl aromatic monomer and thevinyl cyanide monomer are co-polymerized by suspension polymerization. Aconventional polymerization initiator such as azobisisobutyronitrile orbenzoyl peroxide may be used. Likewise, the suspension agent may be aconventional one such as polyvinyl alcohol, polyacrylamide or bariumsulfate. The polymerization temperature is usually within a range offrom 60° to 160° C., and the polymerization time is determined dependingupon the polymerization temperature and the type and amount of theinitiator, but, is usually within a range of from 1 to 10 hours. Inorder to maintain the content of the vinyl cyanide monomer residue inthe resulting copolymer to be constant, the vinyl aromatic monomer orthe vinyl cyanide monomer may be added continuously or intermittently.Further, in order to reduce the amount of the resulting copolymer or toreduce the monomers remaining in the copolymer, stripping may beconducted to recover the monomers.

Then, to this suspension system, an aromatic amine and ammonia are addedto convert the maleic anhydride residue of the copolymer to its imide.The total moles of the aromatic amine and ammonia to be added arepreferably from 0.8 to 1.5 times the moles of the maleic anhydride used.The moles of the aromatic amine are required to be greater than themoles of the ammonia. If the moles of the added amine exceeds 1.5 times,unreacted amine will remain in the composition thus obtained, and if itis less than 0.8 time, the conversion to imide will be inadequate, suchbeing undesirable. The reaction temperature for the conversion to imideis preferably from 120° to 160° C., and the reaction time is preferablyfrom 0.5 to 3 hours. The ammonia may be added in the form of a gas or anaqueous solution (i.e. aqueous ammonia).

Thus, a heat resistant resin composition in the form of particles(beads) wherein the copolymer A and the copolymer B are uniformly mixed,is obtainable. According to the process of the present invention, it isunnecessary to use the N-aromatic maleimide and maleimide which areexpensive and which are not prepared by mass-production, and it isunnecessary to mechanically kneading the copolymer A and the copolymer Bsince the product is obtainable in the form wherein such copolymers arealready uniformly mixed. Thus, industrial merit of this process isextremely great.

Now, the present invention will be described in further detail withreference to Examples. Various physical properties of the compositionswere measured in accordance with the following methods.

Tensile strength and Izod impact strength: JIS K-6871

Heat resistance (Vicat softening point): JIS K-6870

High temperature stability: A test piece was maintained in a gear ovenat 270° for 1 hour, whereupon the presence or absence of foaming and theweight reduction were measured.

EXAMPLE 1

Into a 20 l autoclave, 5710 g of styrene and 189 g of maleic anhydridewere fed, and the temperature was raised to 110° C. under stirring in anitrogen atmosphere. While continuously adding to this system liquidmaleic anhydride in a total amount of 1143 g maintained at a temperatureof 70° C. at a supply rate as shown in the following Table 1, bulkpolymerization was conducted at 110° C. for 220 minutes. At thecompletion of the continuous addition, the conversion was 55% by weightand the content of the maleic anhydride residue in the resultingcopolymer was 33%. To this system, 1200 g of acrylonitrile was added in20 minutes, while lowering the temperature of the system to 95° C., andthe stirring was continued for further 10 minutes at this temperature.At this stage, the concentration of the maleic anhydride in the monomerswas not more than 0.1%.

To this system, 3 g of a polyvinyl alcohol-type suspension agent, 3 g ofa polyacrylic acid ester-type suspension agent and 6500 g of watercontaining 30 g of sodium sulfate were added to bring the system in asuspension state. To this suspension, 4 g of azobisisobutyronitrile wasadded, and polymerization was conducted at 80° C. for 90 minutes. Thetemperature was raised to 150° C. in 60 minutes, and stripping wasconducted for 60 minutes at this temperature. Then, 1140 g of anilineand 116 g of 30% aqueous ammonia were added thereto, and the reactionfor the conversion to imide was conducted at a temperature of 155° C.for 120 minutes. The obtained polymer in the form of beads was washedwith water and then dried.

The beads were analyzed and found to be a mixture comprising 58% byweight of a copolymer A composed of 30% of the N-phenylmaleimideresidue, 3% of the maleimide residue and 67% of the styrene residue, and42% by weight of a copolymer B composed of 40% of the acrylonitrileresidue and 60% of the styrene residue.

The beads were pelletized by a 1 inch extruder equipped with a vent, andthen formed into test pieces by a 1 ounce injection molding machine.Various physical properties of the test pieces were evaluated, and theresults are shown in Table 2.

                  TABLE 1                                                         ______________________________________                                        Supply rate of maleic anhydride                                               Time (min.) Supply rate (g/min.)                                                                        Total amount (g)                                    ______________________________________                                         0          7.0            0                                                   60         5.9           388                                                 120         5.0           715                                                 180         4.2           992                                                 220         3.8           1,143                                               ______________________________________                                    

EXAMPLE 2

Beads were prepared in the same manner as in Example 1 except that theamount of aniline was changed to 885 g and the amount of 30% aqueousammonia was changed to 270 g.

The composition of the beads was found to be a mixture comprising 57% byweight of a copolymer A composed of 23% of the N-phenylmaleimideresidue, 10% of the maleimide residue and 67% of the styrene residue,and 43% by weight of a copolymer B composed of 40% of the acrylonitrileresidue and 60% of the styrene residue. The physical properties areshown in Table 2.

EXAMPLE 3

64 parts by weight of the pellets of Example 2 were mixed with 36 partsby weight of an ABS resin (styrene residue: 49% by weight, acrylonitrileresidue: 17% by weight, and butadiene residue: 34% by weight) preparedby emulsion polymerization, and the mixture was pelletized and formedinto test pieces. Various physical properties of the test pieces wereevaluated. The results thereby obtained are shown in Table 2.

COMPARATIVE EXAMPLE 1

Beads were prepared in the same manner as in Example 1 except that noaniline and no ammonia were added.

The composition of the beads were found to be a mixture comprising 53%by weight of SMA composed of 33% of the maleic anhydride residue and 67%of the styrene residue, and 47% by weight of a copolymer B composed of40% of the acrylonitrile residue and 60% of the styrene residue. Thephysical properties are shown in Table 2.

COMPARATIVE EXAMPLE 2

Beads were prepared in the same manner as in Example 1 except that theamount of aniline was changed to 506 g, and the amount of 30% aqueousammonia was changed to 500 g.

The composition of the beads was found to be a mixture comprising 55% byweight of a copolymer composed of 13% of the N-phenylmaleimide residue,20% of the maleimide residue and 67% of the styrene residue, and 45% byweight of a copolymer B composed of 40% of the acrylonitrile residue and60% of the styrene residue. The physical properties are shown in Table2. While the test pieces of Examples 1 and 2 were transparent, the testpieces of this Comparative Example were opaque, thus indicating that thecompatibility of the copolymers A and B was lost.

COMPARATIVE EXAMPLE 3

Various properties of the commercially available AS resin (SAN-Cmanufactured by Mitsubishi Monsanto Chemical Company) were evaluated,and the results are shown in Table 2.

COMPARATIVE EXAMPLE 4

46 parts by weight of the AS resin used in Comparative Example 3 wasmixed with 36 parts by weight of the ABS resin used in Example 3, andthe mixture was pelletized and then formed into test pieces. Variousphysical properties of the test pieces were evaluated. The resultsthereby obtained are shown in Table 2.

COMPARATIVE EXAMPLE 5

A composition was obtained in the same manner as in Example 1 exceptthat the amount of aniline was changed to 1260 g, and the amount of 30%aqueous ammonia was changed to 0.

This composition was found to be a mixture comprising 58% by weight of acopolymer composed of 31% of the N-phenylmaleimide residue, 2% of themaleic anhydride residue and 67% of the styrene residue, and 42% byweight of a copolymer composed of 40% of the acrylonitrile residue and60% of the styrene residue. The physical properties of the test piecesof this Comparative Example are shown in Table 2. In the case where nomaleimide residue was present, the Vicat softening point decreased byabout 10° C. as compared with the case where the maleimide residue ispresent.

COMPARATIVE EXAMPLE 6

A composition was obtained in the same manner as in Example 1 exceptthat the amount of aniline was changed to 0 and the amount of 30%aqueous ammonia was changed to 770 g.

This composition was found to be a mixture comprising of 53% by weightof a copolymer A composed of 29% of the maleimide residue, 4% of themaleic anhydride residue and 67% of the styrene residue, and 47% byweight of a copolymer B composed of 40% of the acrylonitrile residue and60% of the styrene residue.

The test pieces containing no N-phenylmaleimide residue was opaque andbrittle, and the compatibility of the copolymers A and B was therebycompletely lost.

                  TABLE 2                                                         ______________________________________                                               Examples   Comparative Examples                                               1    2      3      1    2    3    4    5                               ______________________________________                                        Tensile  680    680    500  670  610  720  470  700                           strength                                                                      (Kg/cm.sup.2)                                                                 Izod impact                                                                            1.4    1.4    14.0 1.3  0.9  1.8  15.0 1.5                           strength                                                                      (Kg cm/cm)                                                                    Vicat    133    137    123  131  136  100   98  125                           softening                                                                     point (°C.)                                                            High                                                                          temperature                                                                   stability                                                                     Foaming  No     No     No   Yes  No   No   No   No                            Weight   0.9    0.9     1.0 3.8  0.9  0.9   1.0 1.0                           reduction                                                                     (wt. %)                                                                       ______________________________________                                    

We claim:
 1. A heat resistant resin composition comprising from 10 to90% by weight of a copolymer A and from 90 to 10% by weight of acopolymer B, in which the copolymer A is composed of an N-aromaticmaleimide monomer residue, a maleimide monomer residue wherein the Natom of said maleimide is bonded to a hydrogen atom, a vinyl aromaticmonomer residue and, optionally an other vinyl monomer residue, thetotal content of the N-aromatic maleimide monomer residue and themaleimide monomer residue being from 10 to 45%, the content of theN-aromatic maleimide monomer residue being greater than the content ofthe maleimide monomer residue, the content of the vinyl aromatic monomerresidue being from 90 to 55% and the content of said other vinyl monomerresidue being from 0 to 20%, and the copolymer B is composed of a vinylcyanide monomer residue, a vinyl aromatic monomer residue and,optionally an other vinyl monomer residue, the content of the vinylcyanide monomer residue being from 20 to 55%, the content of the vinylaromatic monomer residue being from 80 to 45% and the content of saidother vinyl monomer residue being from 0 to 20%.
 2. The heat resistantresin composition according to claim 1 wherein the vinyl aromaticmonomer residue is a residue derived from a vinyl aromatic compoundselected from the group consisting of styrene, α-methyl styrene,p-methyl styrene, t-butyl styrene, a styrene halogenide and a mixturethereof.
 3. The heat resistant resin composition according to claim 1wherein the vinyl cyanide monomer residue is a residue derived from avinyl cyanide compound selected from the group consisting ofacrylonitrile, methacrylonitrile and a mixture thereof.
 4. The heatresistant resin composition according to claim 1 wherein the N-aromaticmaleimide residue is a residue of N-aromatic maleimide obtained bycondensation of a primary aromatic amine with fumaric acid, maleic acid,maleic acid anhydride or other maleic acid derivative.
 5. The heatresistant resin composition according to claim 4 wherein the primaryaromatic amine is selected from the group consisting of aniline,toluidine, nitro aniline, phenylenediamine and α-naphthyl amine.
 6. Theheat resistant resin composition according to claim 1 wherein themaleimide monomer residue is a residue derived from maleimide obtainedby condensation of ammonia with maleic acid anhydride.
 7. The heatresistant resin composition according to claim 1 wherein said othervinyl monomer residue is a residue derived from a monomer selected fromthe group consisting of acrylonitrile, methacrylonitrile, methylacrylate, methyl methacrylate, maleic acid anhydride, dimethyl maleateand dimethyl fumarate.